This project is focused on the identification of factors that could alter human susceptibility to bioweapons agents. This is an important goal, as we need to be able to identify high-risk groups in order to target effective preventive measures. Our work to date has resulted in several important findings: 1) the existence of a high degree of inter-individual variation in human innate immune responses to a diverse range of innate immune agonists, 2) determined that a large proportion of this inter-individual variation is due to heritable factors, 3) the identification of numerous common genetic variants within genes of the tolllike receptor (TLR) response pathway that are highly associated with innate immune responses measured in vitro, 4) the identification of a highly functional genetic variant in the gene for TLR1 that dramatically alters TLR1-mediated responses and predicts organ dysfunction and death in patients with sepsis and septic shock. The studies proposed in this renewal will continue to address the Primary Hypothesis: Inter-individual variability in innate immune responses to potential bioweapons agents such as Y. pestis is modified by specific genetic variants, which influence host susceptibility to infection. Over the course of the prior funding period we have enrolled and characterized innate immune responses to a large panel of agonists in over 800 healthy volunteers for whom we have also collected genomic DNA samples. We will employ this unique resource in addition to proposed core resources as part of this RCEB application to further our understanding of how genetic factors modify human host susceptibility to infection. In Aim 1 we will perform a genome-wide association study to identify novel genetic factors predicting very high or very low whole blood cytokine responses to TLR4, TLR7/8, and NOD2 agonists ex vivo. In Aim 2 we will determine the effect of genetic polymorphisms in TLR pathway-related genes on the response of monocytes and alveolar macrophages to infection with select agents in vitro. Finally, in Aim 3 we will determine the role of human TLR1 polymorphisms on infection with Y.pestis and F.tularensis in vivo in mice. Through these proposed studies will gain important new insights into the genetic control of innate immune responses to bacterial products from important select agents and how these genetically controlled responses affect host responses to live pathogens in vitro and in vivo.